Foul-Resistant Condenser Using Microchannel Tubing

ABSTRACT

A condenser coil for a refrigerated beverage and food service merchandiser includes a plurality of parallel flat, multichannel heat transfer tubes and a plurality heat transfer fins extending between adjacent tubes in a generally V-shaped zig-zag pattern. In order to reduce the likelihood of fouling by the bridging of fibers therebetween, the fins are spaced apart at a dimension, w, as measured from apex to apex, of at least about 0.25 inches. In an embodiment, the plurality of heat transfer fins extend between adjacent tubes in a generally V-shaped zig-zag pattern at a spacing, as measured from apex to apex, in the range of from about 0.4 to about 0.8 inches. In an embodiment, the plurality heat transfer fins extend between adjacent tubes in a generally V-shaped pattern at a spacing, as measured from apex to apex, in range of from about ⅓ inches to about ½ inches.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of and is acontinuation-in-part of co-pending U.S. patent application Ser. No.11/255,426, filed Oct. 21, 2005, entitled FOUL-RESISTANT CONDENSER USINGMICROCHANNEL TUBING, and published on Jul. 6, 2006, as U.S. PatentPublication No. 2006-0144076A1, which is a continuation-in-part ofco-pending U.S. patent application Ser. No. 10/835,031, filed Apr. 29,2004, entitled FOUL-RESISTANT CONDENSER USING MICROCHANNEL TUBING, nowU.S. Pat. No. 7,000,415.

BACKGROUND OF THE INVENTION

This invention relates generally to refrigerated beverage and foodservice merchandisers and, more particularly, to a foul resistantcondenser coil therefor.

It is long been the practice to sell soda and other soft drinks by wayof vending machines or coin operated refrigerated containers fordispensing single bottles of beverages. These machines are generallystand alone machines that are plugged into standard outlets and includetheir own individual refrigeration circuit with both evaporator andcondenser coils.

This self serve approach has now been expanded to include other types of“plug in” beverage and food merchandisers that are located inconvenience stores, delicatessens, supermarkets and other retailestablishments.

In such stores, cold beverages, such as soft drinks, beer, wine coolers,etc. are commonly displayed in refrigerated merchandisers forself-service purchase by customers. Conventional merchandisers of thistype usually comprise a refrigerated, insulated enclosure defining arefrigerated product display cabinet and having one or more glass doors.The beverage product, typically in cans or bottles, single or insix-packs, is stored on shelves within the refrigerated display cabinet.To purchase a beverage, the customer opens one of the doors and reachesinto the refrigerated cabinet to retrieve the desired product from theshelf.

Beverage merchandisers of this type necessarily include a refrigerationsystem for providing the cooled environment within the refrigerateddisplay cabinet. Such refrigeration systems include an evaporator coilhoused within the insulated enclosure defining the refrigerated displaycabinet and a condenser coil and compressor housed in a compartmentseparate from and exteriorly of the insulated enclosure. Cold liquidrefrigerant is circulated through the evaporator coil to cool the airwithin the refrigerated display cabinet. As a result of heat transferbetween the air and the refrigerant passing in heat exchangerelationship in the evaporator coil, the liquid refrigerant evaporatesand leaves the evaporator coil as a vapor. The vapor phase refrigerantis then compressed in the compressor coil to a high pressure, as well asbeing heated to a higher temperature as a result of the compressionprocess. The hot, high pressure vapor is then circulated through thecondenser coil wherein it passes in heat exchange relationship withambient air drawn or blown across through the condenser coil by a fandisposed in operative association with the condenser coil. As a result,the refrigerant is cooled and condensed back to the liquid phase andthen passed through an expansion device which reduces both the pressureand the temperature of the liquid refrigerant before it is circulatedback to the evaporator coil.

In conventional practice, the condenser coil comprises a plurality ofround tubes with parallel fins extending between tubes across the flowpath of the ambient air stream being drawn or blown through thecondenser coil. A fan, disposed in operative association with thecondenser coil, passes ambient air from the local environment throughthe condenser coil. U.S. Pat. No. 3,462,966 discloses a refrigeratedglass door merchandiser having a condenser coil with staggered rows offinned tubes and an associated fan disposed upstream of the condensercoil that blows air across the condenser tubes. U.S. Pat. No. 4,977,754discloses a refrigerated glass door merchandiser having a condenser coilwith in-line finned tube rows and an associated fan disposed downstreamof the condenser that draws air across the condenser tubes.

One problem that occurs with such self-contained merchandisers is thatthey are often in area that is heavily trafficked by people that tend totrack in debris and dirt from the outside. This, in turn, tends toexpose the condenser coil, which is necessarily exposed to the flow ofair in the immediate vicinity, to be susceptible to airside fouling.With such fouling, the accumulation of dust, dirt and oils impederefrigeration performance. As the condenser coil fouls, the compressorrefrigerant pressure rises, which leads to system inefficiencies andpossibly compressor failure. Further, such products are often used inlocations where periodic cleaning is not likely to occur.

The usual structure for such a condenser coil is a tube and fin designwherein a plurality of serpentine tubes with refrigerant flowing thereinare surrounded by orthogonally extending fins over which the cooling airis made to flow by way of a fan. Generally, the greater the tube and findensities, the more efficient the performance of the coil in cooling therefrigerant. However, the greater the tube and fin densities, the moresusceptible it is to being fouled by the accumulation of dirt and fiber.

This problem has been addressed in one form by the elimination of finsand relying on conventional tubes as set forth in U.S. Pat. No.6,851,271, assigned to the assignee of the present application andincorporated herein by reference. A further approach has been toselectively stagger the successive rows of tubes in relation to thedirection of airflow as described in U.S. Patent Application No.(PCT/US03/12468), Continuation In Part Application of ProvisionalApplication Ser. No. 60/376,486 filed on Apr. 30, 2002, assigned to theassignee of the present application and incorporated herein byreference.

U.S. Pat. No. 6,988,538 discloses a fin-and-tube condenser coil for usein connection with retail store refrigeration systems wherein thecondenser coil includes a plurality of parallel flat microchannel tubeshaving zig-zag fins extending between adjacent flat tubes. The findensity ranges from slightly less than 12 fins per inch to slightly morethan 24 fins per inch. The high fin density is possible because thecondenser coil is generally position outside the store, such as on theroof-top, where the condenser coil is not exposed to a high level ofdust and debris.

U.S. Pat. No. 6,912,864 discloses a refrigerated display merchandiserhaving a fin-and-tube evaporator formed of a plurality of parallel, flatmicrochannel tubes having V-shaped fins extending between adjacent flattubes. The fin density ranges from as low as 6 fins per inch to as highas 25 fins per inch. The high fin density is possible because theevaporator coil is positioned internally within the rear air duct of therefrigerated merchandiser and therefore not exposed to a high level ofdust and debris

SUMMARY OF THE INVENTION

In one aspect of the invention, a refrigerated merchandiser is providedhaving a condenser coil connected in refrigerant flow communication withan evaporator coil disposed in operative association with the displaycabinet of the refrigerated merchandiser, wherein the condenser coil hasa plurality of refrigerant carrying members aligned in generallyparallel relationship and a plurality of fins connected in heat transferrelationship with and extending between adjacent members of theplurality of refrigerant carrying members, the plurality of fins beingspaced apart at a spacing of at least 0.4 inches between adjacent fins.In one embodiment, the fins are spaced apart at a spacing of at least0.6 inches. In another embodiment, the fins are spaced apart at aspacing in the range of 0.4 to 0.8 inches. In a further embodiment, thefins are spaced apart at a spacing in the range of 0.7 to 0.8 inches.

In one embodiment of the invention, the condenser coil has a pluralityof fins extending generally orthogonally relative to said plurality ofrefrigerant carrying members and being disposed in generally parallelrelationship. In another embodiment, the condenser coil has a pluralityof generally V-fins being spaced apart at a spacing of at least 0.4inches between adjacent fins as measured from apex to apex.

In one embodiment of the invention, the plurality of refrigerantcarrying members of the condenser coil are flat tubes aligned ingenerally parallel relationship with each tube having a plurality oflongitudinally extending channels that are fluidly connected at a firstend to receive refrigerant flow from an inlet header and at a second endto discharge refrigerant flow to an outlet header. In another embodimentof the invention, the plurality of refrigerant carrying members is aserpentine tube having a plurality of flat tube segments aligned ingenerally parallel relationship with adjacent tube members beinginterconnected at their respective ends to form a serpentine refrigerantflow path. The serpentine tube has a plurality of longitudinallyextending channels that are fluidly connected at a first end to receiverefrigerant flow from an inlet header and at a second end to dischargerefrigerant flow to an outlet header.

In another aspect of the invention, a refrigerated merchandiser isprovided having a condenser coil connected in refrigerant flowcommunication with an evaporator coil disposed in operative associationwith the display cabinet of the refrigerated merchandiser, wherein thecondenser coil includes at least one serpentine shaped refrigerant tubehaving a plurality of flat segments aligned in generally parallelrelationship, the plurality of flat segments being spaced apart at aspacing of at least 0.4 inches between adjacent flat segments. Each ofthe flat tube segments of the serpentine shaped refrigerant tube mayinclude a plurality of longitudinally extending channels providing acorresponding plurality of refrigerant flow passages, which may beminichannel or microchannel flow passages. In one embodiment, the flattube segments are spaced apart at a spacing of at least 0.6 inchesbetween adjacent flat segments. In another embodiment, flat tubesegments are spaced apart at a spacing of at least 0.4 to 0.8 inchesbetween adjacent flat segments. In a further embodiment, the flat tubesegments are spaced apart at a spacing of at least 0.6 inches betweenadjacent flat segments.

In one aspect of the invention, a refrigerated merchandiser is providedhaving a condenser coil connected in refrigerant flow communication withan evaporator coil disposed in operative association with the displaycabinet of the refrigerated merchandiser, wherein the condenser coil hasa plurality of refrigerant carrying members aligned in generallyparallel relationship and a plurality of fins connected in heat transferrelationship with and extending between adjacent members of theplurality of refrigerant carrying members in a zig-zag arrangement, thatis a generally V-shaped pattern, with the plurality of fins being spacedapart at a dimension, w, as measured from apex to apex, of at leastabout 0.4 inches. In one embodiment, the fins are spaced apart at aspacing of at least 0.6 inches. In another embodiment, the fins arespaced apart at a spacing in the range of about 0.4 to about 0.8 inches.

In another aspect of the invention, a refrigerated merchandiser isprovided having a condenser coil connected in refrigerant flowcommunication with an evaporator coil disposed in operative associationwith the display cabinet of the refrigerated merchandiser, wherein thecondenser coil has a plurality of refrigerant carrying members alignedin generally parallel relationship and a plurality of fins connected inheat transfer relationship with and extending between adjacent membersof the plurality of refrigerant carrying members in a zig-zagarrangement, that is a generally V-shaped pattern, with the plurality offins being spaced apart at a dimension, w, as measured from apex toapex, in range of from about ⅓ inches to about ½ inches.

In another aspect of the invention, a refrigerated merchandiser isprovided having a condenser coil connected in refrigerant flowcommunication with an evaporator coil disposed in operative associationwith the display cabinet of the refrigerated merchandiser, wherein thecondenser coil has a plurality of flat, multichannel refrigerantcarrying tubes aligned in generally parallel relationship and aplurality of fins connected in heat transfer relationship with andextending between adjacent members of the plurality of refrigerantcarrying members in a zig-zag arrangement, that is a generally V-shapedpattern, with the plurality of fins being spaced apart at a dimension,w, as measured from apex to apex, of at least 0.25 inches.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the invention, reference will be made tothe following detailed description of the invention which is to be readin connection with the accompanying drawings.

FIG. 1 is a perspective view of a refrigerated beverage merchandiser inaccordance with the prior art.

FIG. 2 is a sectional, side elevation view of the refrigerated beveragemerchandiser showing the evaporator and condenser sections thereof.

FIG. 3 is a perspective view of a condenser coil in accordance with oneembodiment of the present invention.

FIG. 4 is a graphic illustration of the relationship between tube/findensity and occurrence of fouling.

FIG. 5 is a perspective view of an alternative embodiment of a condensercoil in accordance with the present invention.

FIG. 6 is a side sectional view of a tube support arrangement inaccordance with one embodiment of the invention.

FIG. 7 is a front view thereof.

FIG. 8 is an alternative embodiment of the invention showing staggeredrows of microchannel tubes.

FIG. 9 is an alternate embodiment of a condenser coil in accordance withthe invention.

FIG. 10 is an alternate embodiment of the invention showing anembodiment of the invention with V-shaped fins.

FIG. 11 a is an enlarged elevation view of a one-inch length segment ofa conventional round tube, parallel fin condenser having a fin densityof 4 fins per inch illustrating a characteristic fouling patternthereof.

FIG. 11 b is an enlarged elevation view of a one-inch length segment ofan exemplary embodiment of a flat tube, V-shaped fin pattern condenserin accord with invention having a fin density of 4 fins per inchillustrating a characteristic fouling pattern thereof.

FIG. 11 c is an enlarged elevation view of a one-inch length segment ofan exemplary embodiment of a flat tube, V-shaped fin pattern condenserin accord with invention having a fin density of 5 fins per inchillustrating a characteristic fouling pattern thereof.

FIG. 11 d is an enlarged elevation view of a one-inch length segment ofan exemplary embodiment of a flat tube, V-shaped fin pattern condenserin accord with invention having a fin density of 6 fins per inchillustrating a characteristic fouling pattern thereof.

FIG. 11 e is an enlarged elevation view of a one-inch length segment ofan exemplary embodiment of a flat tube, V-shaped fin pattern condenserin accord with invention having a fin density of 8 fins per inchillustrating a characteristic fouling pattern thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2, there is depicted therein a refrigeratedcold beverage merchandiser generally designated by the numeral 10. Thebeverage merchandiser 10 includes an enclosure 20 defining arefrigerated display cabinet 25 and a separate utility compartment 30disposed externally of and heat insulated from the refrigerated displaycabinet 25. The utility compartment may be disposed beneath therefrigerated display cabinet 25 as depicted or the utility compartmentmay be disposed above the display cabinet 25. A compressor 40, acondenser coil 50, a condensate pan 53 and an associated condenser fanand motor 60 are housed within the compartment 30. A mounting plate 44may be disposed beneath the compressor 40, the condenser coil 50, andthe condenser fan 60. Advantageously, the mounting plate 44 may beslidably mounted within the compartment 30 for selective dispositioninto and out of the compartment 30 in order to facilitate servicing ofthe refrigeration equipment mounted thereon.

The refrigerated display cabinet 25 is defined by an insulated rear wall22 of the enclosure 20, a pair of insulated side walls 24 of theenclosure 20, an insulated top wall 26 of the enclosure 20, an insulatedbottom wall 28 of the enclosure 20 and an insulated front wall 34 of theenclosure 20. Heat insulation 36 (shown by the looping line) is providedin the walls defining the refrigerated display cabinet 25. Beverageproduct 100, such as for example individual cans or bottles or six packsthereof, are displayed on shelves 70 mounted in a conventional mannerwithin the refrigerated display cabinet 25, such as for example inaccord with the next-to-purchase manner shown in U.S. Pat. No.4,977,754, the entire disclosure of which is hereby incorporated byreference. The insulated enclosure 20 has an access opening 35 in thefront wall 34 that opens to the refrigerated display cabinet 25. Ifdesired, a door 32, as shown in the illustrated embodiment, or more thanone door, may be provided to cover the access opening 35. It is to beunderstood however that the present invention is also applicable tobeverage merchandisers having an open access without a door. To accessthe beverage product for purchase, a customer need only open the door 32and reach into the refrigerated display cabinet 25 to select the desiredbeverage.

An evaporator coil 80 is provided within the refrigerated displaycabinet 25, for example near the top wall 26. An evaporator fan andmotor 82, as illustrated in FIG. 2, may be provided to circulate airwithin the refrigerated display cabinet 25 through the evaporator 80.However, the evaporator fan is not necessary as natural convection maybe relied upon for air circulation through the evaporator. As thecirculating air passes through the evaporator 80, it passes in aconventional manner in heat exchange relationship with refrigerantcirculating through the tubes of the evaporator coil and is cooled as aresult. The cooled air leaving the evaporator coil 80 is directeddownwardly in a conventional manner into the cabinet interior to passover the product 100 disposed on the shelves 70 before being drawn backupwardly to again pass through the evaporator.

Refrigerant is circulated in a conventional manner between theevaporator 80 and the condenser 50 by means of the compressor 40 throughrefrigeration lines forming a refrigeration circuit (not shown)interconnecting the compressor 40, the condenser coil 50 and theevaporator coil 80 in refrigerant flow communication. As noted before,cold liquid refrigerant is circulated through the evaporator coil 80 tocool the air within the refrigerated display cabinet 25. As a result ofheat transfer between the air and the refrigerant passing in heatexchange relationship in the evaporator coil 80, the liquid refrigerantevaporates and leaves the evaporator as a vapor. The vapor phaserefrigerant is then compressed in the compressor 40 to a high pressure,as well as being heated to a higher temperature as a result of thecompression process. The hot, high pressure vapor is then circulatedthrough the condenser coil 50 wherein it passes in heat exchangerelationship with ambient air drawn or blown across through thecondenser coil 50 by the condenser fan 60.

Referring now to FIG. 3, in accordance with the present invention, thetube and fin condenser coil 50 of FIG. 2 is replaced by a microchannelcondenser coil as shown generally at 110. Here, rather than round tubes,a plurality of microchannel tubes 111, having a plurality of parallelchannels 112 extending the length thereof, are provided in parallelrelationship in a row 115 and are connected at their respective ends byinlet and outlet headers 113 and 114, respectively. An inlet line 116 isprovided at the inlet header 113 and the outlet line 117 is provided atthe outlet header 114. In operation, the hot, high pressure refrigerantvapor is passed from the compressor into the inlet line 116 where it isdistributed to flow, by way of the individual microchannels 112, througheach of the microchannel tubes 111 to be condensed to a liquid state.The liquid refrigerant then flows to the outlet header 114 and out theoutlet line 117 to the expansion device.

In order to increase the heat exchange capacity of the coil 110, aplurality of fins 118 may be placed between adjacent microchannel tubepairs. These fins are preferably aligned orthogonally to themicrochannel tube 111 and parallel with the direction of airflow throughthe microchannel condenser coil 110. The lateral spacing betweenadjacent fins is the dimension “W”.

One advantage offered by the microchannel tube 111 over the conventionalround tubes in a condenser coil is that of obtaining more surface areaper unit volume. That is, generally, a plurality of small tubes willprovide more external surface area than a single large tube. This can beunderstood by comparison of a single ⅜ inch (8 millimeter) tube with a 5millimeter tube. The external surface area-to-volume ratio of the 5millimeter tube is 0.4, which is substantially greater than that for a 8millimeter tube, which is 0.25.

One disadvantage to the use of a greater number of smaller tubes ratherthan fewer larger tubes is that it is generally more expensive toimplement. However, the techniques that have been developed formanufacturing microchannel tubes with a plurality of channels hasevolved to the extent that they are now economical as compared with themanufacturer and implementation of round tubes in a heat exchanger coil.Another advantage of the microchannel tubes is that they are morestreamlined so as to result in a lower pressure drop and lower noiselevel. That is, there is much less resistance to the air flowing overthe relatively narrow microchannels than there is to the air flowingover relatively large round tubes.

Considering now the problem of air side fouling which results from theaccumulation of dust, dirt and oils between adjacent tubes and/oradjacent fins of a condenser coil, the applicants have recognized thatsuch a fouling starts with the bridging of an elongate fiber betweenadjacent tubes or between adjacent fins. That is, most small particleswill pass through the passages of a coil unless a passage is somewhatblocked by the lodging of a fiber therein. When a bridging fiber islodged between adjacent fins or adjacent tubes, then small particlestend to collect on that fiber with the build up eventually resulting ina fouling of the passageway. In order to prevent or reduce theoccurrence of fouling, it is therefore necessary to understand themanner in which the bridging effect is influenced by the structuralconfiguration of the coil. With that in mind, the applicants haveconducted experimental tests to determine how the variation in thespacing of the tubes and the spacing of the fins can affect the tendencyof fouling to occur. The results are shown in FIG. 4.

A field analysis was conducted to determine the types of material thatwere most likely to cause fouling in the condenser coil, and it wasfound that cotton fibers were the predominant cause of the foulings andthat fouling is generally started by the bridging of an elongate fiberbetween adjacent fin or between adjacent tubes. Accordingly,experimental analysis was conducted to determine the fouling tendenciesof a condenser coil in an environment of cotton fibers as the spacing ofthe fins is selectively varied. A number of heat exchangers, each beingof a standard design with round tubes and plate fins of a specificspacing were exposed to an environment of natural cotton fibers andtested for their relative tendencies to foul. A heat exchanger havingseven fins per inch, or a fin spacing of 0.14 inches between adjacentfins, was arbitrarily assigned a fouling goodness parameter (FGP) of 1.This is shown at point A on the graph of FIG. 4.

As the fin spacing is increased, the associated increase in FGP issubstantially linear to point B where the spacing is 0.40 inches and theFGP is 1.5. At point C, the relationship is still close to linearwherein the spacing is point 0.50 inches with an associated FGP of 2,which means that the heat exchanger is twice as “good” as compared tothe heat exchanger at Point A in regards to fouling.

As the front spacing is increased beyond the 0.50 spacing, it will beseen that the FGP begins to increase substantially beyond the linearrelationship, and at a spacing of 0.75 inches as shown at point B, itapproaches an asymptotic relationship. Thus, it can be concluded thatideally, the fin spacing should be maintained at 0.75 inches or greaterif the maximum FGP is desired. At those higher spacing parameters,however, it will be recognized that the exposed surface area is reducedand therefore the heat exchange capability is also reduced. Accordingly,it may be desirable to maintain sufficient fin spacing so as to obtain asufficiently high FGP while, at the same time, maintaining sufficientdensity to provide a desired amount of surface area. For example, atpoint E, a sufficiently high FGP of 6 is obtained with a fin spacing of0.70 inches between adjacent fins.

Although the experiential data as discussed hereinabove relates to finspacing on round tube heat exchangers, the applicants believe that thesame performance characteristics will be true of fin spacing with amicrochannel tubing heat exchanger as shown in FIG. 3 since theprincipals involving the attachment of elongate fibers will besubstantially the same in each case. Further, recognizing that with amicrochannel tubing arrangement as shown in FIG. 3, it is possible toeliminate the fins entirely, or to reduce the number such that they aresimply provided for support between the microchannel tubes, while at thesame time increasing the density of the microchannel tubes to obtain thedesired surface area for heat exchange purposes. Such a heat exchangeris shown in FIG. 5.

In the FIG. 5 embodiment, it will be seen that the fins have beeneliminated and the microchannel tubes 111 are simply cantileveredbetween the inlet header 113 and outlet header 114 as shown. With thisarrangement, the construction is very much simplified, and the expenseof the fins is eliminated. However, the benefit of having the surfacearea of the fin is also lost for heat transfer purposes. Accordingly, itmay be necessary to increase the density of the microchannel tubing 111such that the distance therebetween, shown as L in FIG. 5 issubstantially reduced. In this regard, the considerations discussedhereinabove, with respect to the spacing of fins is also considered tobe relevant with respect to the spacing of the microchannel tubes 111.That is, with the spacing L of 0.75 inches, there will be little or nofouling that occurs, and as that fin density is increased, the foulinggoodness parameter (FGP) will be decreased or, said in another way, theprobability of fouling will be increased.

With the complete elimination of fins as shown in FIG. 5, it may benecessary to provide some support between adjacent microchannel tubes111, so that both during the manufacture of the heat exchanger and inthe finished product, the microchannel tubes 111 are restrained fromsagging from their relative parallel positions. Such a support is shownat 118 in FIGS. 6 and 7. In FIG. 6, the support member 118 with itsplurality of teeth 119 is shown in the uninstalled position at the leftand then in the installed position at the right. In FIG. 7, there isshown in a side elevational view and a front view, three such supportmembers 118 in their installed positions. Such a support member 118 maybe fabricated of a heat conductive material so as to not only providesupport but also act as a conductor in the same manner as a fin.However, with the significant spacing as shown, so as to notsignificantly add to the heat conduction surface area, the benefit ofthe fin effect is minimal. Accordingly, the support members may as wellbe made of other materials such as a plastic material which will providethe necessary support but not contribute to the function of heattransfer. Here, the spacing of the support members 118 is clearlysufficient such that the lateral space between the support members willnot contribute to the bridging of fibers that would cause fouling.Rather, it is only the distance L between adjacent microchannel tubesthat will allow for the bridging of fibers therebetween. Theconsiderations discussed with respect to the FIG. 5 embodiment aretherefore relevant to the supported embodiment of FIGS. 6 and 7.

With the elimination of the fins as discussed hereinabove, anothereffect that must be considered is that with the resulting reduced heatexchange surface area, and with an associated increase in the density ofthe microchannel tubes, will there be still sufficient heat exchangesurface area to obtain the necessary performance? Presuming that,because of the performance characteristics discussed hereinabove, thespacing L between adjacent microchannels tubes is maintained at around0.75 inches, the resulting number of microchannel tubes may not besufficient to bring about the desired amount of heat exchange. Oneapproach for overcoming this problem is shown in FIG. 8 wherein a secondrow 121 of microchannel tubes 122 is shown with its associated header123. This will, in effect, double the surface area of the heat exchangerwithout significantly adding to the problem of fouling betweenmicrochannel tubing. While the two rows 115 and 121 of microchanneltubes can be aligned one behind the other in the direction of theairflow, the airflow characteristics can be improved by staggering thetwo rows such that the tubes 122 of the second row are disposedsubstantially between, but downstream of, the tubes 111 of the first row115. With such an arrangement, the controlling parameter with respect tothe fouling resistant parameter is still the distance L since this isthe distance not only between the individual tubes 111 of the first row115 but also between the tubes 122 of the second row 121. That is, withsuch a staggered relationship, there is very little likelihood of afiber tending to bridge the gap between a tube 111 in the first row 115and a tube 122 in the second row 121.

It will, of course, be understood that multiple rows of tubes can beplaced in such a staggered relationship such that the third row wouldmost likely be aligned with the first row and a fourth row would be mostaligned with a second row and so forth. Again, the fouling goodnessparameter would not significantly change since the controlling parameterwould still be the distance L between tubes in any single row.

Referring now to FIG. 9, there is depicted an alternate embodiment ofthe condenser coil of the invention designated generally as 120. In thisembodiment, rather than being formed of a plurality of parallellydisposed, flat multi-channel tubes 111 extending longitudinally betweencommon inlet and outlet headers 113 and 114 as in the condenser coil 110depicted in the FIG. 5 embodiment of the invention, the condenser coil120 is formed of at least one serpentine, flat multichannel tube 130having a plurality of parallelly disposed, flat tube segments 131interconnected by tube bends 132 to form a serpentine tube extendingbetween an inlet header (not shown) connected in flow communication toone end thereof and an outlet header (not shown) connected in flowcommunication to the other end thereof. The parallelly disposed, flatmultichannel tube segments 131 of the condenser coil 120 are generallyaligned with the direction of airflow thereover and are spaced apartwith a spacing L between adjacent tubes similarly to the flat tubes 111of FIG. 5 embodiment of the condenser coil. For the reasons discussedhereinbefore, to provide a satisfactory fouling goodness parameter, thespacing L between adjacent flat tube segments should be at least 0.4inches. In an embodiment, the flat tube segments are spaced apart at adistance in the range of 0.4 to 0.8 inches. In another embodiment, theflat tube segments are spaced apart at a distance of at least 0.6inches. In another embodiment, the flat tube segments are spaced apartat a distance in the range of 0.4 to 0.8 inches. For the reasonsdiscussed hereinbefore, to provide a satisfactory fouling goodnessparameter, the spacing L between adjacent flat tubes 111 or flat tubesegments 131 should be at least 0.4 inches. In an embodiment, the flattubes or tube segments are spaced apart at a distance in the range of0.4 to 0.8 inches. In another embodiment, the flat tubes or tubesegments are spaced apart at a distance of at least 0.6 inches. As notedhereinbefore, the multichannel tubes 111 and 130 have a plurality ofparallel channels extending the length thereof to provide multiplerefrigerant flow passages therethrough. The channels may be of circularor non-circular cross-section. In condenser coils for refrigeratedmerchandisers, the individual channels typically would have a hydraulicdiameter, defined as 4 times the flow area divided by the perimeter, ofabout 1 millimeter to about two millimeters, but may have a hydraulicdiameter as large as about 5 millimeters and as small as about 200microns.

In the embodiment depicted in FIG. 9, only one serpentine tube is shown.It is to be understood that in practice, the condenser coil 120 mayinclude a plurality of serpentine tubes 130 extending between therespective inlet and outlet headers and being disposed in axially spacedrelationship with respect to airflow through the condenser coil. Theserpentine tubes could be disposed in alignment or in a staggeredrelationship, such as discussed hereinbefore with respect to theembodiment of the condenser coil depicted in FIG. 8. In operation, thehot, high pressure refrigerant vapor from the compressor is passed to aninlet header (not shown) where it is distributed to flow, by way of theindividual channels of the serpentine multichannel tube or tubes 130,through each of tubes 130 to be condensed to a liquid state. The liquidrefrigerant is collected in an outlet header (not shown) and flowstherefrom through the refrigerant circuit to the expansion device andthence on to an evaporator. Similarly, although depicted in FIG. 10 ashaving only one tube bank, the condenser 140 may have a plurality oftube banks extending between respective inlet and outlet headersdisposed in axially spaced relationship with respect to airflow throughthe condenser coil and disposed in alignment or in staggeredrelationship, such as discussed hereinbefore with respect to theembodiment of the condenser coil depicted in FIG. 8.

In the embodiment depicted in FIG. 9, the condenser coil 120 is formedof at least one serpentine, flat multichannel tube 130 having aplurality of parallelly disposed, flat tube segments 131 having aplurality of generally V-shaped fins 128 extending between adjacent tubesegments 131 in a zig-zag pattern. In the embodiment depicted in FIG.10, the condenser coil is formed of a plurality of parallelly disposed,flat multi-channel tubes 111, which extend longitudinally between commoninlet and outlet headers 113 and 114, having a plurality of generallyV-shaped fins 128 extending between adjacent tubes 111 in a zig-zagpattern. The parallel disposed, flat multichannel tube segments 131 ofthe condenser coil 120 and the parallel disposed, flat multichanneltubes 111 of the condenser coil 140 are generally aligned with thedirection of airflow thereover and are spaced apart with a spacing Lbetween adjacent tubes.

The condensers of the invention depicted in FIGS. 9 and 10 have aplurality of fins 128 arranged in a zig-zag pattern, instead of beingparallelly disposed. For similarly spaced fin arrangements, zig-zag orgenerally V-shaped fin arrangements provide more fin surface area perunit of width across the condenser coil than do parallelly disposedfins. It is to be understood that the term “generally V-shaped fins”includes not only the actual V-shaped pattern fin arrangements depictedin FIGS. 9 and 10, but also similar zig-zag pattern fin configurations,such as for example, but not limited to, sinusoidal waveform fins andother generally U-shaped waveform fins. The plurality of generallyV-shaped arranged fins 128 extend between adjacent multichannel tubes,as depicted in FIG. 10, or between parallel tube segments of aserpentine multichannel tube of the type depicted in FIG. 9. These finsare preferably aligned parallel with the direction of airflow throughthe multichannel condenser coil. In zig-zag or generally V-shapedpattern arrangements, the fin spacing, that is the dimension “w”, ismeasured from apex to apex as illustrated in FIGS. 9 and 10.

Referring now to FIG. 11 a, there is depicted an exemplary foulingpattern on a conventional round tube, parallel fin condenser having afin density of 4 fins per inch of the type commonly installed instand-alone refrigerated merchandisers found in supermarkets and othercommercial establishments. As illustrated, dust and debris tend toaccumulate in the corners where the flat fins 8 meet orthogonally withthe round tubes 11, resulting in not only the surface of the fins beingfouled, but also the surface of the heat transfer tube being fouled.This type of fouling pattern results in a degradation of the heattransfer efficiency of the condenser.

Referring now to FIGS. 11 b-11 e, representative characteristic foulingpatterns are depicted for various exemplary embodiments of flat tube,finned condensers according to the present invention. As notedhereinbefore, rather than being arranged in a parallel arrayorthogonally to the heat transfer tube as in the conventional condenserdepicted in FIG. 11 a, in the condenser of the refrigerated merchandiserof the present invention, the heat transfer fins 128 are arranged in azig-zag or V-shaped pattern at a spacing, w, as measured from apex toapex and meet with the flat multichannel heat transfer tubes 111, orsegments 131, at an acute angle, rather than orthogonally. In theembodiments depicted in FIGS. 11 b, 11 c and 11 d, the heat transferfins 128 are arranged at a fin spacing, w, as measured from apex toapex, of ½ inch (0.5 inches), 4/10 inch (0.4 inches) and ⅓ inch (0.33inches), respectively, providing respective fin densities of four fins128 per inch (FIG. 11 b), of five fins 128 per inch (FIG. 11 c) and ofsix fins 128 per inch (FIG. 11 c).

In the embodiment depicted in FIG. 11 e, the heat transfer fins 128 arearranged in a zig-zag or V-shaped pattern at a fin spacing, w, asmeasured from apex to apex of 0.25 inches, thereby providing arelatively high fin density of 8 fins per inch. At this relatively highfin density, the fouling is significantly more severe than in theembodiments illustrated in FIGS. 11 b, 11 c and 11 e, but not much moresevere than the fouling characteristic of the round tube, parallel fincondenser on a refrigerated merchandiser in a supermarket or retailstore environment as illustrated in FIG. 11 a. Further, a condenserhaving flat heat transfer tubes with the eight fin per inch finarrangement depicted in FIG. 11 e would be substantially more foulresistant than a condenser having round heat transfer tubes withparallel fins at an eight fin per inch density.

As illustrated in FIGS. 11 a-11 e, in zig-zag arrangements, the dust,debris and other fouling material 125 tend to collect more prominentlyin the apex between intersecting fins 128. Thus, the surface of the heattransfer tube remains relatively free of fouling. Further, because thefins 128 extend a longer length between the heat transfer tubes thanwould orthogonal fins 118 extending between similarly space tubes, thereis a significantly greater likelihood of a greater portion of the finsurface remaining relatively foul free. Accordingly, the heat transferefficiency of the flat tube, V-shaped fin pattern condensers of theinvention depicted in FIGS. 11 b, 11 c, 11 d and 11 e will be superior,at comparable fin densities, to the heat transfer efficiency of theconventional round tube, parallel fin pattern condensers commonly usedin conventional refrigerated merchandisers, particularly when used in ahigh fouling inducing environment, such as for example the environmentwithin most supermarkets and retail stores.

In general, to provide a satisfactory fouling goodness parameter in ahigh fouling inducing environment, the flat heat transfer tube condenserof the invention will have heat transfer fins extending between adjacenttubes in a zig-zag or generally V-shaped pattern at a spacing, w, asmeasured from apex to apex, in the range of ⅓ inches to ½ inches orgreater. In an embodiment, the generally V-shaped fins are spaced apartat a distance of at least about 0.4 inches apex to apex. In anembodiment, the generally V-shaped fins are spaced apart at a distancein the range of 0.4 to 0.8 inches apex to apex. In another embodiment,the generally V-shaped fins are spaced apart at a distance of at least0.6 inches apex to apex. In applications subject to a somewhat lesserfouling environment, the generally V-shaped fins may be spaced apart ata distance of as little as ¼ inches apex to apex.

As noted hereinbefore, the multichannel tubes 111 and 130 have aplurality of parallel channels extending the length thereof to providemultiple refrigerant flow passages therethrough. The channels may be ofcircular or non-circular cross-section. In condenser coils forrefrigerated merchandisers, the individual channels typically would havea hydraulic diameter, defined as 4 times the flow area divided by theperimeter, of about 1 millimeter to about two millimeters, but may havea hydraulic diameter as large as about 5 millimeters and as small asabout 200 microns.

While the present invention has been particular shown and described withreference to preferred and alternate embodiments as illustrated in thedrawings, it will be understood by one skilled in the art that variouschanges in detail may be effective therein without departing from thetrue spirit and scope of the invention as defined by the claims.

1. A refrigerated merchandiser comprising: an enclosure defining arefrigerated display cabinet and having an access opening for providingaccess to the refrigerated display cabinet; an evaporator coil disposedin operative association with the refrigerated display cabinet; and acondenser coil connected in refrigerant flow communication with saidevaporator coil, said condenser coil having a plurality of refrigerantcarrying members aligned in generally parallel relationship and aplurality of fins connected in heat transfer relationship with andextending between adjacent members of said plurality of refrigerantcarrying members, said plurality of fins being spaced apart at a spacingof at least 0.4 inches between adjacent fins.
 2. A refrigeratedmerchandiser as recited in claim 1 wherein said plurality of finscomprises a plurality of fins extending generally orthogonally relativeto said plurality of refrigerant carrying members and being disposed ingenerally parallel relationship.
 3. A refrigerated merchandiser as setforth in claim 2 wherein said plurality of fins are spaced apart in therange of 0.4 to 0.8 inches between adjacent fins.
 4. A refrigeratedmerchandiser as set forth in claim 2 wherein said plurality of fins arespaced apart at a spacing of at least 0.6 inches between adjacent fins.5. A refrigerated merchandiser as set forth in claim 2 wherein saidplurality of fins are spaced apart in the range of 0.7 to 0.8 inchesbetween adjacent fins.
 6. A refrigerated merchandiser as set forth inclaim 2 wherein said plurality of fins are spaced apart substantially0.75 inches between adjacent fins.
 7. A refrigerated merchandiser asrecited in claim 1 wherein said plurality of fins comprises a pluralityof generally V-fins being spaced apart at a spacing of at least 0.4inches between adjacent fins as measured from apex to apex.
 8. Arefrigerated merchandiser as set forth in claim 7 wherein said pluralityof fins are spaced apart in the range of 0.4 to 0.8 inches betweenadjacent fins as measured from apex to apex.
 9. A refrigeratedmerchandiser as set forth in claim 7 wherein said plurality of fins arespaced apart at a spacing of at least 0.6 inches between adjacent finsas measured from apex to apex.
 10. A refrigerated merchandiser as setforth in claim 7 wherein said plurality of fins are spaced apart in therange of 0.7 to 0.8 inches between adjacent fins as measured from apexto apex.
 11. A refrigerated merchandiser as set forth in claim 7 whereinsaid plurality of fins are spaced apart substantially 0.75 inchesbetween adjacent fins as measured from apex to apex.
 12. A refrigeratedmerchandiser as set forth in claim 1 wherein said plurality ofrefrigerant carrying members comprises a plurality of flat tubes alignedin generally parallel relationship, each tube having a plurality oflongitudinally extending channels that are fluidly connected at a firstend to receive refrigerant flow from an inlet header and at a second endto discharge refrigerant flow to an outlet header.
 13. A refrigeratedmerchandiser as set forth in claim 12 wherein said flat tubes are spacedin the range of 0.4 to 0.8 inches between adjacent tubes.
 14. Arefrigerated merchandiser as set forth in claim 12 wherein said flattubes are spaced in the range of 0.7 to 0.8 inches between adjacenttubes.
 15. A refrigerated merchandiser as set forth in claim 12 whereinsaid flat tubes are spaced substantially 0.75 inches between adjacenttubes.
 16. A refrigerated merchandiser as set forth in claim 1 whereinsaid plurality of refrigerant carrying members comprises a serpentinetube having a plurality of flat tube segments aligned in generallyparallel relationship with adjacent tube members being interconnected attheir respective ends to form a serpentine refrigerant flow path, theserpentine tube having a plurality of longitudinally extending channelsthat are fluidly connected at a first end to receive refrigerant flowfrom an inlet header and at a second end to discharge refrigerant flowto an outlet header.
 17. A refrigerated merchandiser as set forth inclaim 16 wherein said flat tube segments are spaced at a spacing of atleast 0.6 inches between adjacent tube segments.
 18. A refrigeratedmerchandiser as set forth in claim 16 wherein said flat tube segmentsare spaced in the range of 0.4 to 0.8 inches between adjacent tubesegments.
 19. A refrigerated merchandiser as set forth in claim 16wherein said flat tube segments are spaced in the range of 0.7 to 0.8inches between adjacent tube segments.
 20. A refrigerated merchandiseras set forth in claim 1 wherein each of said plurality of refrigerantcarrying members comprises a flat tube segments having a plurality oflongitudinally extending channels defining flow passages, each channelhaving a hydraulic diameter of about 1 millimeter to about 2millimeters.
 21. A refrigerated merchandiser comprising: an enclosuredefining a refrigerated display cabinet and having an access opening forproviding access to the refrigerated display cabinet; an evaporator coildisposed in operative association with the refrigerated display cabinet;and a condenser coil connected in refrigerant flow communication withsaid evaporator coil, said condenser coil having at least one serpentineshaped refrigerant carrying member having a plurality of flat segmentsaligned in generally parallel relationship, said plurality of flatsegments being spaced apart at a spacing of at least 0.4 inches betweenadjacent flat segments.
 22. A refrigerated merchandiser as recited inclaim 21 wherein said flat tube segments are spaced apart at a spacingof at least 0.6 inches between adjacent flat segments.
 23. Arefrigerated merchandiser as recited in claim 21 wherein said flat tubesegments are spaced apart at a spacing in the range of 0.4 to 0.8 inchesbetween adjacent flat segments.
 24. A refrigerated merchandiser asrecited in claim 21 wherein said flat tube segments are spaced apart ata spacing in the range of 0.7 to 0.8 inches between adjacent flatsegments.
 25. A refrigerated merchandiser as recited in claim 21 whereineach of said flat tube segments has a plurality of longitudinallyextending channels providing a corresponding plurality of refrigerantflow passages.
 26. A refrigerated merchandiser as recited in claim 25wherein each of said channels has a hydraulic diameter in the range fromabout 200 microns to about 5 millimeters.
 27. A refrigeratedmerchandiser comprising: an enclosure defining a refrigerated displaycabinet and having an access opening for providing access to therefrigerated display cabinet; an evaporator coil disposed in operativeassociation with the refrigerated display cabinet; and a condenser coilconnected in refrigerant flow communication with said evaporator coil,said condenser coil having a plurality of refrigerant carrying membersaligned in generally parallel relationship and a plurality of generallyV-shaped fins connected in heat transfer relationship with and extendingbetween adjacent members of said plurality of refrigerant carryingmembers, said plurality of generally V-shaped fins being spaced apart ata spacing of at least 0.25 inches between adjacent fins.
 28. Arefrigerated merchandiser as set forth in claim 27 wherein saidplurality of fins are spaced apart in the range of about 0.4 to about0.8 inches between adjacent fins as measured from apex to apex.
 29. Arefrigerated merchandiser as set forth in claim 27 wherein saidplurality of fins are spaced apart at a spacing of about ⅓ to about ½inches between adjacent fins as measured from apex to apex.
 30. Arefrigerated merchandiser as set forth in claim 27 wherein saidplurality of refrigerant carrying members comprises a plurality of flattubes aligned in generally parallel relationship, each tube having aplurality of longitudinally extending channels that are fluidlyconnected at a first end to receive refrigerant flow from an inletheader and at a second end to discharge refrigerant flow to an outletheader.
 31. A refrigerated merchandiser as set forth in claim 30 whereinsaid flat tubes are spaced in the range of 0.4 to 0.8 inches betweenadjacent tubes.
 32. A refrigerated merchandiser as set forth in claim 30wherein said flat tubes are spaced in the range of 0.7 to 0.8 inchesbetween adjacent tubes.
 33. A refrigerated merchandiser as set forth inclaim 30 wherein said flat tubes are spaced substantially 0.75 inchesbetween adjacent tubes.
 34. A refrigerated merchandiser as set forth inclaim 27 wherein said plurality of refrigerant carrying memberscomprises a serpentine tube having a plurality of flat tube segmentsaligned in generally parallel relationship with adjacent tube membersbeing interconnected at their respective ends to form a serpentinerefrigerant flow path, the serpentine tube having a plurality oflongitudinally extending channels that are fluidly connected at a firstend to receive refrigerant flow from an inlet header and at a second endto discharge refrigerant flow to an outlet header.
 35. A refrigeratedmerchandiser as set forth in claim 34 wherein said flat tube segmentsare spaced at a spacing of at least 0.6 inches between adjacent tubesegments.
 36. A refrigerated merchandiser as set forth in claim 34wherein said flat tube segments are spaced in the range of 0.4 to 0.8inches between adjacent tube segments.
 37. A refrigerated merchandiseras set forth in claim 34 wherein said flat tube segments are spaced inthe range of 0.7 to 0.8 inches between adjacent tube segments.
 38. Arefrigerated merchandiser as set forth in claim 27 wherein each of saidplurality of refrigerant carrying members comprises a flat tube segmentshaving a plurality of longitudinally extending channels defining flowpassages, each channel having a hydraulic diameter of about 1 millimeterto about 2 millimeters.
 39. A refrigerated merchandiser as recited inclaim 38 wherein each of said channels has a hydraulic diameter in therange from about 200 microns to about 5 millimeters.
 40. A refrigeratedmerchandiser comprising: an enclosure defining a refrigerated displaycabinet and having an access opening for providing access to therefrigerated display cabinet; an evaporator coil disposed in operativeassociation with the refrigerated display cabinet; and a condenser coilconnected in refrigerant flow communication with said evaporator coil,said condenser coil having a plurality of refrigerant carrying membersaligned in generally parallel relationship and a plurality of finsconnected in heat transfer relationship with and extending betweenadjacent members of said plurality of refrigerant carrying members, saidplurality of fins being arranged in a zig-zag pattern and spaced apartat a spacing in the range of from ⅓ inches to ½ inches apex to apex.